Full Cell Study of Diels Alder Poly(phenylene) Anion and Cation Exchange Membranes in Vanadium Redox Flow Batteries

Abstract

In this work, we report on the performance of Diels Alder poly(phenylene) membranes in vanadium redox flow batteries. The membranes were functionalized with quaternary ammonium groups to form an anion exchange membrane (QDAPP) and with sulfonic acid groups to form a cation exchange membrane (SDAPP). Both membrane classes showed similar conductivities in the battery environment, suggesting that the ion conduction mechanism in the material is not strongly affected by the moieties along the polymer backbone. The resistance to vanadium permeation in QDAPP was not improved relative to SDAPP, further suggesting that the polarity of the functional groups do not play a significant role in the membrane materials tested. Both QDAPP and SDAPP outperformed Nafion membranes in cycling tests, with both achieving voltage efficiencies above 85% while maintaining 95% coulombic efficiency while at a current density of 200 mA/cm 2 . © The Author The need for grid-scale energy storage is well-established as demand for intermittent renewable energy sources increases. Among grid-scale energy storage technologies, vanadium redox flow batteries (VRFBs) present an attractive option, as has been extensively discussed elsewhere.1-4 One of the key components in VRFBs is the membrane. As the separator between the positive and negative sides, the membrane is responsible for limiting undesired crossover of vanadium species and water while enabling ion conduction. The membrane's ability to restrict crossover is the key factor in cell coulombic efficiency and is important in slowing capacity fade. The conductivity determines the ohmic drop in the membrane, which is the major source of ohmic resistance in the battery and therefore plays a key role in determining voltage loss.5 Thus, it is desirable to engineer membranes that have a high selectivity, i.e., low vanadium permeability with high conductivity for charge carrying ions, predominantly protons or bisulfate. Commonly used membrane materials in the laboratory consist of perfluorinated polymers that provide chemical-mechanical stability, with polar side chains to provide ion conduction pathways; however, materials such as Nafion are relatively expensive and exhibit poor selectivity. Modified Nafion membranes can provide improved selectivity, 6,7 but are still based on the expensive Nafion material. Several studies have investigated alternative hydrocarbon backbone polymers as a means to decrease cost and improve selectivity. Proton exchange membranes in the form of sulfonated aromatic polymers have received the most attention 1,9-13 due to the relative ease of preparation and promising VRFB performance. However, issues of low membrane cyclic lifetimes have been reported and suggest membrane oxidation through the VO 2 + ion. 14 Therefore, anion exchange membranes (AEM) have been presented as an attractive option because vanadium permeation is expected to be limited by the Donnan potential generated by the positively charged functional groups, which would not only reduce vanadium crossover, bu...

Hydrophilic microporous membranes for selective ion separation and flow-battery energy storage

“…(~$500 per m 2 ), dominate, despite suffering from poor selectivity due to swelling in water. Intensive research efforts have developed low-cost hydrocarbon-based polymer electrolyte membranes 5,19,20,21 , for example, polyaromatic ionomers with pendant ionic functional groups demonstrate promising performance in vanadium flow batteries 22,23 and fuel cells [24][25][26] . Ion transport within these polymers depends on the formation of nanoscale interconnected water channels via microphase separation of the hydrophobic backbone and hydrophilic side chains, 29 which is a complex process that is difficult to control on a molecular level.…”

Vanadium Redox Flow Batteries: A Review Oriented to Fluid-Dynamic Optimization

“…In these cases and taking advantage of the lower requirements of the organic electrolyte, commercial membranes of lower cost are the most common used, see the work of Hu et al [74]. According to Pezeshki et al [76], membranes of the polyarylene type, either anionic or cationic, show remarkable properties in comparison to commercial membranes based on perfluorosulfonic polymers. However, chemical stability is usually a challenge for such materials.…”

The Structure–Activity Relationship in Membranes for Vanadium Redox Flow Batteries

“…To solve the problems, AEMs with various polymer backbones have been studied for VRFBs. Various polyketones like poly(ether ether ketone) (PEEK), poly(phthalazinone ether ketone) (PPEK), poly(phthalazinone ether ketone ketone) (PPEKK), poly(aryl ether ketone) (PAEK), cardo‐poly(ether ketone) (PEK‐C), polysulfones like poly(arylene ether sulfone) (PAES), poly(ether sulfone) (PES), polysulfone (PSF or PSU), and poly(phenyl sulfone) (PPSU), polyolefins like Diels Alder poly(phenylene) (DAPP), polyethers like poly(fluorenyl ether) (PFE) and poly (ethylene) (PE), and poly(benzimidazole) (PBI)95a,100 have been developed as polymer backbones for VRFBs.…”

“…The mechanical stability of membrane depends on the structure of polymer backbone. To avoid the degradation of backbone, the quaternized DAPP membranes with fully aromatic structure was synthesized for VRFBs . The backbone of DAPP showed better stability than other polyaromatics like PAEs due to the absence of aryl‐ether linkages .…”